Purification of aryl disulfides



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INVENTORS MARUN B. NEUWORTH By JOHN c. PATERsoN ATTORNEY United States Patentr i' 'PURIFICATION 0F ARYL DISULFIDES Martinl1Neuworth, Pittsburgh, Pa., .lohn C. Paterson, New City, NSY., `and 'Richard P. Tarhox, Westfield, NJ., assignors to Consolidation `Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Application May 8, 1957, Serial No. 657,768

`8 Claims. (Cl. 260'608) The present invention relates to the removal of impuri- .ties .from ,aryl .disuldes More particularly, the inveny.tion relates toanl aqueous acetic acid Washing treatment .to remove .inorganic .contaminants from aryl disultldes.

Aryl disulfides are those chemical Vcompounds having the following structural formula:

'the aqueous .phase and permit .their y'separate recovery.`

When the cresylic acids thereafter are subjected to an oxodizing treatment, the aryl hydrosuliides `(lthiophenol, thiocresols and thioxylenols) tend 'tocouple whereby aryl thioxylenols.

- vPatented Sept. 15, 1959 faice `free of copper and manganese to permit .their :use .as l.rub-

lIber reclaiming reagents.

In addition, the aryl disuliides `frequently contain quantities of low boiling organic sulfur compounds and .neu- .tral oils lwhich are objectionable because .of their foul odor. It is desirable that vthese low boiling `sulfur .com-

j-pounds are .neutral oils .be removed -from lthe .aryl Adisul- One Yobvious way to veliminate both types .oficontarn- `inants is by distillation .of .the aryl disulfides. fln fact, vacuum distillation on a laboratory .scalehas been emi- 'nently vsatisfactory for .this purpose. Extensive exposure of -aryl disuldes to elevated temperatures causes are- 'version of the disuldes toaryl'hydrosuldes Whichis undesirable. Their distillation, accordingly, must Ibe carried out at short residence times under .high vacuum.

' f HoWever,-on a commercial scale .the vacuum .distillation disulfides are formed. The phenolic ingredients of the.

oxidized cresylic acids can be .recovered thereafter in a purified .condition by Van aqueous 'caustic lwash. The aryl disuldes remain undissolved in the aqueous caustic and .can :be recovered by :decantation y These aryl .disuldes ihave yfound utility as rubber re-. claiming reagents. :A solution of .the aryl .disultdes in a high boiling oil is effective to depolymerize vulcanized vrubber 'to 4permit `reuse 'of the rubber b y revulcariization The reclaimed rubber `frequently is yblended with ycrude rubber prior to vulcanization.

rllhe inorganic contaminants'found in crude aryl disult :fides can be .detected analytically as an ash :remaining .after combustion of vla ysample of .the .crude material.

The inorganic contaminants :frequently include copper which 4may appear .as y,finely divided particleslof-metal-or K @raides ,oras salts. .Copper .usually .is introduced :into-the aryl disuldes during copper sweetening .processes employed in petroleum refineries. In addition, the aryl disuliides `frequently contain .manganese in the form of nely divided particles of metal or oxides or as salts.,

'The manganese usually .is introduced into .the aryl ldisuldes during the oxidation .treatment employed to `form 'thedisulides from the 'hydrosuldes Manganese compounds are used asa catalyst'for the oxidation 1('.U.`S." Pat ents 1,993,287 and 2,035,121). Both copper and Inanganese are notorious poisons in the rubber compounding art. They tend to promoteoxidation of rubber products. Accordingly, aryl disuldes which contain copper or manganese cannot 'be 'employed as'rubber reclaiming` reagents. e v

Hence it is essential 'that aryl ldisulfides be'su'bstantially .aryl .disulfdes .soluble metallic acetates which remain in the 4aqueous .acetic acid phase and are .thereby removed from the technique introducesextraordinary .expenses into the .Cost ofpreparingaryl disuldes satisfactory for use as a rubber reclaiming agent.

We have found, according to the .present invention, .thatthe copper and manganese .can be virtually eliminated from faryl disulfides .by .an .aqueous acetic acid washing treatment. Aqueous acetic vacid is immiscible with the The copper and manganese form wateraryl disulfide liquid by decantation. The aryl disuliides, thus purified, can be freed of the low Iboiling sulfur c ornpounds and any residual acetic acid by a lsimple linexpensive steam stripping treatment.

It is an object olf this invention to provide ka process for removing inorganic contaminants, especially objectionable copper and manganese from .liquid aryl disultides by .an aqueous acetic `acid washing treatment. A further object of this invention -is to remove .low boiling sulfur compounds, neutral oils and residual acetic ,acid from .aryl `disuliides by .a steam Astripping treatment.

`For a completelunderstanding ofthetpresent invention, its objects and advantages, reference should beha-to the accompanying drawing Awhich 'is a `schermati@ ilow diagram rillustrating apparatus adapted to Ipractice the :pres- .ent .'invention.

'Referring .to the drawing, a storage vessel lll lis provided as a surge vessel lfor the aryl `disulfide/s with which the process .is concerned. A quantity of .aryl -dsultldes is withdrawn from the storage .vessel '16 through a valyed .conduit 1l and lpuiiired through mechanical lters 12 which serve to remove any mechanical impurities Sin the Starting material. Mechanical impurities might vinclude metallic particles, Catalyst particles and pitchlilic inaterials frequently foundiin aryl disuliides which have been stored for .extended periods. The filtration step clariiies the aryl disuliides `andproducesa light colored material as filtrate. The characteristic black color of crude aryl disuldes results from a suspension of minute pitchlillce .particles therein. Aryl disuldes lare recovered as lil- `trate through a valve dconduit 13 and arepumped into a mixing and settling vessel 14.

Aqueous acetic acid isprovideddn a storage vessel .115. APreferably the concentration of the acetic yacid Yis from about l to "20 percent acetic acid in water. 'The aqueous acetic .acid is introduced vinto the mixing `and ksettling vessel 1.4 through a'valved conduit 16. Aboutj to 2O pounds of aqueous acetic acid are .employed per IDO pounds of aryl disuldes in the mixing and .Settling wissel '14. .In a preferred embodiment .we employ forCCh 11'00 `-pounds of aryl disulfidesabout 2.5 pounds of a 5 percent .forms a supernatant aqueous phase. jIntimatembiing/of the two phases is eected within the mixing and settling Vliquid-vapor contacting apparatus.

t s f vessel 14. Conveniently the mixing can be accomplished by bubbling air upwardly through the liquid phases from a conduit 17 which is provided in the base of the mixing and settling vessel 14. If desired, mechanical agitation may be provided.

The agitation is continued for a period of about 1 to 20 hours. Following the agitation period, the phases are permitted to separate. Most of the inorganic material, especially the copper and manganese, appears in the aqueous acetic acid phase. The organic phase, containing the aryl disulfides, is withdrawn from the mixing and settling vessel 14 through a valved conduit 18 and is pumped through a valved conduit 19, a heat exchanger 20 and a valved conduit 21 into a steam stripper 22. Within the heat exchanger 20 the aryl disulfides are elvated in 'temperature to about 100 C., i.e., the boiling point of i water. The stripping also assures a moisture-free product.

The steam stripper 22 may comprise any type of A tray tower is schematically illustrated in the drawing. A packed tower also might be employed. From about l to 20 pounds of steam are introduced into the stripper 22 through a conduit 23 located near the bottom of the steam stripper 22. The live steam serves to strip out water, low boiling sulfur compounds and neutral oils from the aryl disulfides which remain in the liquid phase. Any residual acetic acid also passes into the vapor phase along with the y steam. The vapor phase contaminants in steam are recovered overhead from the steam stripper 22 through a conduit 24. A condenser 25 in conduit 24 cools the vapors and condenses them to a liquid phase. The liquid phase is recovered in a condensate vessel 26 from l which a water phase and an oil phase may be recovered separately by decantation.

The liquid phase products from the steam stripper 22 comprise the aryl disuldes which therein have been u freed of low boiling contaminants which are objectionafter the organic phase containing aryl disultides is withdrawn, as described, through the valved conduit 18 and the valved conduit 19, only the aqueous acetic acid phase remains. This phase contains the inorganic contaminants which were removed during the washing treatment. The aqueous acetic acid phase is rejected from the system through valved conduit 18 and a valved conduit 30. This is accomplised by closing the valve in conduit 19 and opening the valve in conduit 30.

Thus the system illustrated in the drawing includes means for removing mechanical impurities, inorganic contaminants and low boiling, foul-smelling sulfur compounds and neutral oils from the aryl disulides.

When the aryl disulfides are to be used as a rubber reclaiming oil, it is desirable to blend the aryl disulfides with a so-called cut back oil. This cut back oil is an extender for the aryl disulfides. High boiling naphthenic and paraffnic oils are satisfactory for this purpose. We have satisfactorily used a parafnic oil having an initial boiling point of 350 C. for this purpose. A supply of cut back oil may be provided in a storage vessel 31. The outback oil is introduced into a product mixing vessel 33 through a valved conduit 32. A supply of aryl disulfides is introduced into the product mixing vessel 33 through a valved conduit 34. From about 1 to 4 volumes of aryl disulfides are employed for each volume of cut back oil. While the aryl disulfides and cut back oil are miscible, some agitation means should be provided to assure uniform blending. Air may be introduced into the product mixing vessel 33 through an air conduit 35 for this pur- V pose. Mechanical agitation may be employed if desired.

The blended product is withdrawn from the product mixing vessel 33 through a valved product Withdrawal conduit 36.

To illustrate the present invention, a number of examples will be presented. In Examples 1 3, a sample of crude aryl disulfides was found to contain 0.13 percent inorganic material (including copper and manganese). These aryl disuldes were obtained from oxidation with manganese oxide catalyst of aryl hydrosulfides. The aryl disulfides, in turn, were obtained as a product from a petroleum refinery employing catalytic cracking processes and a copper sweetening process.

Example 1 The crude aryl disulfides were filtered through a laboratory filter. The filtrate contained 0.13 percent inorganic material. Hence no removal of inorganic contaminants resulted.

Example 2 The crude aryl disuldes were washed With hot Water. The washed organic phase contained 0.13 percent inorganic material. Hence no removal of inorganic contaminants resulted.

Example 3 A. Ash content 0.096 percent B. Quantitative spectrographic analysis:

Ingredient in ash Quantity (percent of sample) Copper 0.002 Manganese 0.007

C. Semi-quantitative spectrographic analysis:

Ingredient in ash- 10 to 100% Iron, sodium. 1 to 10% Calcium. 0.1 to 1.0% Aluminum, chromium, lead,

magnesium, silicon. 0.01 to 0.1% Copper, manganese, nickel,

titanium, vanadium. Less than 0.01% Molybdenum.

The ydescribed crude aryl disuldes were then treated as described in Examples 4 through 8.

Example 4 The crude aryl disulides were washed with lan equal volume of 5 percent hydrochloric acid. The Washed organic phase contained 0.091 percent inorganic material. Hence only about 7 percent of the inorganic contaminants were eliminated. Some reversion of the aryl disuldes to thiophenols also occurred during the treatment.

Example 5 The crude aryl disuliides were washed with an equal volume of 37 percent hydrochloric acid. The washed organic phase contained 0.072 percent inorganic material. Here only about 26 percent of the inorganic contaminants were eliminated. Some reversion of the aryl disulfides to thiophenols also occurred during the treatment.

Example 6 A sample of crude aryl disulfide was washed with aqueous sulfuric acid. The mixture sludged severely. No attempt at product analysis was made.

Examplel Z The crude aryl= disuldes were washed with anA equal volume of 5 percent solution of acetic acid. The washed aryl disuldes contained 0:037 percent inorganic material.

'Ihus about `6,2,- percent ofv the inorganic contaminants were eliminated. v Analysis of the remaining inorganic material showed thecopper-content to be 0.000015percent and the manganese content to be 0.00002 percent.

Thus the hydrochloric acid (Examples 4 and 5 effected only ia slight reduction in the inorganic content of the aryl disuldes and also effected an undesirable destruction of some of the aryl disuldes. The acetic acid washing (Example 7), on the other hand, removed about 62 percent of the inorganic contaminants and reduced the copper and manganese contamination to an innocuous value. More than 99 percent of the copper was eliminated. About 96 percent of the manganese was removed.

The product of Example 7 was submitted for quantitative spectrographic analysis for copper, manganese, iron and ash. The product also was submitted for semi-quantitative spectrographic analysis 'for other metals. The results were `as follows:

A. Ash content 0.037 percent. B. Quantitative spectrographic analysis:

Ingredient in ash- Quantity (percent of sample) Crude aryl disulides were washed with acetic acid as described in Example 7. The resulting liquid aryl disulfides contained 0.1078 percent of low boiling mercaptans. Live steam was passed through the liquid aryl disulfides and the stripped vapors were removed. About seven parts of steam were used for each part of aryl disuliides. The liquid aryl disuldes remaining showed only a trace of mercaptans or acetic acid. Mercaptan analysis in both instances was conducted by a technique employing ammonium thiocyanate and silver nitrate titration. Mercaptans were found in the condensed steam vapors.

The apparatus illustrated in the accompanying drawing has been described in relation to a batch-wise treating process. The system may be made semi-continuous by providing an additional mixing and settling vessel 14 and, if desired, an additional product mixing vessel 33. The additional vessel would be operated alternately according to the well-known semi-continuous principles.

According to the provisions of the patent statutes, we Ihave explained the principle, preferred construction and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specically illustrated and described.

We claim:

l. 'Ihe method for removing metallic contaminants selected from the group consisting of copper, manganese, sodium, calcium, aluminum, chromium, magnesium and molybdenum from normally liquid aryl disuliides which comprises washing the aryl disulfides with an aqueous acetic acid solution immiscible therewith whereby the relatively. efree of metallic. contaminants separately lfrom the. aqueous acetic, acid. solution. containing, dissolved metallic, contaminants.

2.,"12he1 method for. removing. copper contaminants from normally, liquid aryl, disuliides'. which, comprises washing the aryl disultides with an aqueous acetic acid solution immiscible therewith whereby the copper contaminants are transferred to the aqueous acetic acid solution and recovering the aryl disuliides relatively free of copper separately from the aqueous acetic acid solution containing dissolved copper contaminants.

3. The method for removing manganese contaminants fro-rn normally liquid `aryl disullides which comprises washing the aryl disuliides with an aqueous .acetic acid solution irnmiscible therewith :whereby the manganese contaminants are transferred to the aqueous acetic acid solution and recovering the aryl disuliides relatively free of manganese separately from the aqueous acetic acid solution containing dissolved manganese contaminants.

4. The methoid for purifying normally liquid aryl disuldes containing low boiling sulfur compounds and dissolved metallic contaminants selected from the group consisting of copper, manganese, sodium, calcium, aluminum, chromium, magnesium and molybdenum which ycomprises washing the aryl disuldes with an aqueous acetic acid solution irnmiscible therewith whereby the metallic contaminants are transferred to the aqueous acetic acid solution and recovering the aryl disuliides free of metallic contaminants separately lfrom the aqueous acetic acid solution containing dissolved metallic contaminants, `thereafter passing live steam through said liquid aryl disulfides in a vapor-liquid contacting zone to strip low boiling sulfur compounds and acetic `acid therefrom, recovering eluent steam and vapors from said contacting zone and recovering liquid aryl disullides substantially free of acetic acid and low boiling sulfur compounds therefrom.

5. The method for removing metallic contaminants selected from the group consisting of copper, manganese, sodium, calcium, aluminum, chromium, magnesium and molybdenum from normally liquid aryl disulfides which comprises washing the aryl disuliides with 0.5 to '20 percent ofl its weight of an aqueous solution containing l to 20 percent of acetic acid whereby metallic contaminants are transferred to the aqueous solution and recovering the aryl disultdes relatively free of metallic contaminants separately from the aqueous solution containing dissolved metallic contaminants.

t6. The method for removing copper contaminants `from normally liquid aryl disullides which comprises washing the aryl disuldes with 0.5 to 20 percent of its weight of an aqueous solution containing 1 to 20 percent of acetic acid whereby the lcopper contaminants are transferred to the aqueous solution and recovering the aryl disultides relatively free of copper contaminants separately from the aqueous solution containing dissolved copper contaminants.

7. The method for removing manganese contaminants from normally liquid aryl disuldes which comprises washing the aryl disuliides with 0.5 to 20 percent of .its weight of an aqueous solution containing 1 to 20 percent of acetic acid whereby the manganese contaminants are transferred to the aqueous solution and recovering the disulfides relatively free of manganese contaminants separately from the aqueous solution containing dissolved manganese contaminants.

8. The method for purifying normally liquid aryl disuliides containing low boiling sulfur compounds and metallic contaminants selected from the group consisting of copper, manganese, sodium, calcium, aluminum, chromium, magnesium and molybdenum which comprises Washing the aryl Idisuliides with 0.5 to 20 percent of its weight of an aqueous solution containing l to 20 percent f 7 of acetic acid whereby the metallic .contaminants are steam and vapors from said contacting zone and recovtransferred to `the aqueous solution and recovering the ering liquid aryl disuldes substantially free of acetic aryl disuldes relatively free of metallic contaminants 'acid and low boiling sulfur compounds therefrom. separately from the aqueous solution containing dissolved metallic contaminants, thereafter passing l to 20 pounds 5 RefelellCeS Cited in the le Of this Patent of live steam through each pound of aryl disuldes in a vapor-liquid contacting zone to strip 10W boiling sulfur UNITED STATES PATENTS compounds and acetic acid therefrom, recovering effluent 2,446,231 Johnson Aug. 3', 1948 

1. THE METHOD FOR REMOVING METALLIC CONTAMINANTS SELECTED FROM THE GROUP CONSISTING OF COPPER, MAGNESIUM AND SODIUM, CALCIUM, ALUMINUM, CHROMIUM, MAGNESIUM AND MOLYBDENUM FROM NORMALLY LIQUID ARYL DISULFIDES WHICH COMPRISES WASHING THE ARYL DISULFIDES WITH AN AQUEOUS ACTEIC ACID SOLUTION IMMISCIBLE THEREWITH WHEREBY THE METALLIC CONTAMINANTS ARE TRANSFERRED TO THE AQUEOUS ACETIC ACID SOLUTION AND RECOVERING THE ARYL DISULFIDES RELATIVELY FREE OF METALLIC CONTAMINANTS SEPERATELY FROM THE AQUEOUS ACETIC ACID SOLUTION CONTAINING DISSOLVED METALLIC CONTAMINANTS. 